JPH03118164A - Thermal head driving device - Google Patents

Abstract

PURPOSE:To eliminate a dispersion in heat characteristic of a thermal head by a method wherein a pulse width which is applied to a thermal head is calcu lated based on an input thickness information on a thermal resistance layer. CONSTITUTION:When a facsimile apparatus is adjusted at a manufacturing stage, a thickness information of a glaze layer 2 of a thermal head which is used for a plotter 12 is operation-input by an operation display unit 13. By this method, a control unit 10 reads a pulse width information which has already been stored, according to the thickness information of the glaze layer 2 of the thermal head, which has been input, and informs the pulse width information to the plotter 12. The plotter 12 sets a pulse width for a driving pulse which is applied to the thermal head at the time of recording motion, according to the informed pulse width information. By this method, the plotter 12 can record an image with an approximately uniform quality, regardless of a thickness of the glaze layer 2 of the thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head driving device that drives a thermal head to generate heat.

[Prior Art] A thermal head used as a recording head in a thermal recording type printer, a thermal transfer type printer, etc. has heating elements arranged at a predetermined pitch in the recording width, and an example of the configuration is shown in FIG.

In the figure, a glaze layer 2 made of glass material is laminated on a substrate 1 as a heat resistance layer.

A heating element 3 and electrodes 4 and 5 for applying a driving current to the heating element 3 are formed on the glaze layer 2. The abrasion resistant M6 is for contacting the heat-sensitive recording paper or the dye ribbon and supplying the amount of heat from the heating element 3 to the heat-sensitive recording paper or the dye ribbon.

Then, as shown in FIG. 4(a), when a driving voltage is applied between the electrodes 4 and 5, Joule heat is generated from the heating element 3 in accordance with the current flowing through the heating element 3, and its temperature rises. When the application of the driving voltage is stopped, the generation of Joule heat from the heating element 3 is also stopped, thereby cooling the heating element 3 and lowering its temperature.

At this time, when the heat-sensitive recording paper is not in contact with the wear-resistant layer 6, the temperature of the heating element 3 changes as shown by the solid line in FIG. 4(a).

Furthermore, when the heat-sensitive recording paper is in contact with the wear-resistant layer 6, the amount of heat generated from the heating element 3 is transferred to the heat-sensitive recording paper via the wear-resistant layer 6, so that the temperature of the heat-generating element 3 remains the same. At the same time, the temperature of the part of the thermal recording paper that is in contact with the abrasion resistant layer 6 changes as shown by the broken line in the figure, and the temperature of the thermal recording paper changes to the coloring temperature. During the period Ta exceeding Th, the thermal recording paper develops color.

Now, the amount of heat generated from the heating element 3 is transmitted to the adjacent region via the electrodes 4 and 5 and the glaze layer 2, and is also transmitted to the substrate 1 via the glaze layer 2.
It is transmitted to the heat-sensitive recording paper via the wear-resistant layer 6.

Here, the amount of heat 9. .

Heat amount9. and heat m q P are transferred, when the amount of heat 9 is large and the amount of heat q and the amount of heat q are small, the temperature rise characteristic of the heating element 3 becomes good, and the amount of heat 9 b The larger the value, the better the temperature fall characteristics of the heating element 3 will be.

[Problems to be Solved by the Invention] In general, a material with good thermal conductivity is used as the substrate 1, so that the heat It q b transferred through the glaze layer 2 and the substrate 1 is equal to that of the glaze M2. Determined by heat capacity.

However, this glaze layer 2 has a large variation of about 20% during the manufacturing of the thermal head, so the thermal properties of the glaze layer 2 vary widely, and therefore the thermal properties of the thermal head vary widely, causing unevenness during recording. This could cause some inconvenience.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal head driving device that can eliminate variations in thermal characteristics of a thermal head.

[Means for Solving the Problems] The present invention includes an operation means for inputting thickness information of a heat resistance layer, and a method for applying an electric current to a thermal head based on the thickness information of the heat resistance layer input from the operation means. It is equipped with a control means for calculating the pulse width.

[Function] Therefore, since the driving pulse width of the thermal head is set according to the thickness of the thermal resistance layer (glaze layer) that influences the variation in the characteristics of the thermal head, it is possible to eliminate the variation in the characteristics of the thermal head. can.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, the principle of the present invention will be explained.

According to the inventor's experiments, the thermal response characteristics of the thermal head having the configuration shown in FIG.
The thickness changes as shown in FIG. Here, the pulse width of the driving pulse applied to the thermal head is 1
．． 0 (milliseconds), and the applied energy (heat amount) is 0.5 (watts) per dot. In addition, curves CI, C2, C3, C4, C5, and C6 in the same figure have glaze layer thicknesses of 20.40, 60, 80.100, and
200 (μm) is shown.

Normally, for example, the thickness of the glaze layer of a thermal head used for thermal recording paper such as a plotter of a facsimile machine is 50 (μ11), and assuming that the variation is ±10"1, the thickness of the glaze layer of the thermal head actually used is The thickness of the glaze layer is within the range of 40 to 60 (μm).6 Therefore, if the temperature of the heating element when the temperature of the thermal recording paper rises to the coloring temperature Th is Th', then the heating element When the thickness of the glaze layer is 40 (μm), the time it takes to reach the temperature Th' is the time tb shown in the figure.
In addition, when the thickness of the glaze layer is 50 (μl11), the time t shown in the figure becomes louder. However, t, <t
It is b.

In this way, the temperature characteristics of the thermal head vary depending on the thickness of the glaze layer, so the thickness of the glaze layer is measured in advance, and the pulse width of the driving pulse applied to the thermal head is determined according to the measured value. Then, stable recording operation can be performed using the thermal head regardless of the thickness of the glaze layer.

In addition, in this case, if the thickness of the glaze layer is 40 (μm), the pulse width must be longer than time tb, and if the thickness of the glaze layer is 60 (μIo), the pulse width must be equal to or longer than time tb. Since t1 or more is required, these times ja
+jb can also be defined as, for example, the lower limit value of the pulse width when controlling the pulse width by heat storage control.

FIG. 2 shows a facsimile machine according to an embodiment of the present invention. Note that in the following description, parts not directly related to the present invention are omitted.

In the figure, a control unit 10 controls the operation of the facsimile machine and performs predetermined transmission control procedure processing, a scanner 11 is for reading both JM manuscript images at a predetermined resolution, and a plotter Reference numeral 12 records and outputs images at a predetermined resolution. Further, this plotter 12 is composed of a thermal recording type recording device.

The operation display section 13 consists of various operation keys and a display for operating this facsimile machine.
The encoding/decoding unit 14 encodes and compresses both signals obtained by reading with the scanner 11, and also decodes the encoded and compressed image information into the original image signal.

The modem 15 performs modulation and demodulation processing for transmitting digital data via an analog line network, and the network control unit 16 connects this facsimile device to a telephone line network.

With the above configuration, when adjusting this facsimile apparatus at the manufacturing stage, information on the thickness of the glaze layer of the thermal head used in the plotter 12 is input through the operation display section 13.

It is known that the thickness of the glaze layer of a thermal head has little variation within the same production lot of thermal heads, but varies greatly between different production lots, and the thickness information is provided by the manufacturer of the thermal head. Obtainable.

Therefore, the operator who adjusts the facsimile machine inputs the thickness information of the glaze layer of the thermal head obtained from the manufacturer through the operation display section 13.

Thereby, the control unit 10 reads out the previously stored pulse width information based on the input thickness information of the glaze layer of the thermal head, and notifies the plotter 12 of the pulse width information.

Thereby, the plotter 12 sets the pulse width of the drive pulse applied to the thermal head during the recording operation based on the notified pulse width information.

This allows the plotter 12 to record images of a fairly constant quality regardless of the thickness of the glaze layer of the thermal head.

Further, the relationship between the thickness information of the glaze layer stored in the control unit 10 and the pulse width can be obtained by actually measuring the above-mentioned experiment.

Note that the present invention can be applied not only to thermal heads used in thermal recording type recording apparatuses, but also to thermal heads used in other recording apparatuses.

[Effects of the Invention] As explained above, according to the present invention, the operating pulse width of the thermal head is set according to the thickness of the thermal resistance layer, which influences the variation in the characteristics of the thermal head. This has the effect that variations in characteristics can be eliminated.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between the thickness of the glaze layer and the temperature characteristics of the thermal head, Fig. 2 is a block diagram showing a facsimile machine according to an embodiment of the present invention, and Fig. 3 shows the configuration of the thermal head. The illustrated cross-sectional view, FIG. 4, is a graph diagram illustrating the relationship between the voltage applied to the heating element and the temperature of the heating element. 10... Control section, 13... Operation display section. Figure 1 Figure 1 Figure 1

Claims (1)

[Claims] In a thermal head driving device for driving a thermal head in which a thermal resistance layer is provided between a heating element and a substrate, an operation means for inputting thickness information of the thermal resistance layer;
A thermal head driving device characterized by comprising a control means for calculating a pulse width to be applied to the thermal head based on the thickness information of the thermal resistance layer inputted from the operation means.